1. Field of the Invention
The present invention relates to an information processing apparatus capable of performing a predetermined process, such as scrambling, on tampered stream data.
2. Description of the Related Art
A content recorded on a recording media such as a DVD disk or a hard disk recorder, encryption is performed to protect the content, and status information indicating the encryption status is added to the content data.
In order to secure the content, it is important that the status information indicating encryption status is valid.
For example, a program stream stored on a DVD disk or the like is in a state in which the program stream is scrambled. To play back the program stream, it is necessary descramble the program stream read from the DVD disk.
However, if information described in a header or the like of the scrambled data is tampered with, audio/video data can be played back in an unauthorized manner. For example, if data which should be protected from being copied is subjected to tampering, the data can be freely copied.
To avoid the above problem, when the status information is subjected to tampering, the content is generally protected as follows.
First, in a logical process in the decoding, the status information is checked whether it has been subjected to tampering.
If tampering is detected, this fact is notified to a CPU (control system).
If the CPU receives the notification, the CPU issues a command to a display logic circuit to perform scrambling.